Image forming methods for obtaining a positive image for viewing include the methods described below.
(1) Negative - Positive Method
This is a method which comprises forming a negative image on a photosensitive material which is an intermediate medium by shooting etc., and thereafter forming a positive image on another photographic material from said negative image. Accordingly, this is a method of conducting negative type development of the negative photographic emulsion twice.
(2) Direct Positive Method
This is a method which comprises directly forming a positive image on a final photographic material by shooting etc. without passing through an intermediate medium, and more specifically, this may further be classified into the following two types:
(a) that by the reversal development of a negative photographic emulsion; and
(b) that employing a direct reversal photographic emulsion.
Therefore, where it is contemplated to obtain the so-called photographic prints having positive images from both medium having a negative image (e.g. a color negative film) and medium having a positive image (e.g. a color slide film), then in the former caes of the color negative film, it is necessary to conduct printing on a color photographic paper employing a negative photographic emulsion and then conduct negative type development, while in the latter case of the color slide film, it is necessary to conduct reversal development of a color photographic paper employing a negative photographic emulsion or to employ a color photographic paper employing a direct reversal photographic emulsion. In short, the kind of the photographic materials for prints and the processing methods are completely different depending on whether the image possessed by the original medium is a negative image or a positive image.
The situation described above has heretofore been accepted as a matter of course by those engaged in the photography processing industry; however, in fact, it is extremely troublesome and very inefficient to change the photographic material and the processing method depending on the kind of the image possessed by the original medium (hereinafter referred to as "the original image"), that is, whether it is a positive image or a negative image.